Effects once per turn?

I don't understand one thing about "once per turn".

Why can z. B. The cyber dragon infinity if it is on the field twice, activate it twice (cancel a card effect) although it only says once per turn.

If I z. B summoning elementary hero sunrise twice in one turn, I'm not allowed to look for miraculous fusion twice…

Does anyone know the standard situation?

Source: yu gi oh legacy of the duelist ps4

This is a difference between "hard and soft 'once per turn" effects ".

"Hard once per turn effects" have the name of the card in their effect text, which then counts for all copies of the card.

"Soft once per turn effects" do not have the name of their own card in the effect text and therefore only apply to the actual copy on the field.

With the soft you can use several different cards with the same name, with the hard you can only use the effect once.